A Research Note Nucleic Acid, Purine and Proximate Analyses of Mechanically Separated Beef and Veal DENNIS A. SAVAIANO, LISA M. SALATI, WAYNE D. ROSAMOND, JOEL SALINSKY, and B. WELLS WILLIS ABSTRACT Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), purine (ade- nine, guanine, hypoxanthine and xanthine) and proximate analyses of mechanically separated (MS) beef and veal were conducted to verify and evaluate changes in nucleic acid content which may re- sult from mechanical separation. DNA and total nucleic acid levels were higher in both MS beef and veal whereas RNA levels were higher only in MS beef compared to hand deboned (HD) counter- parts. Adenine, guanine and xanthine levels were higher in MS beef and veal, and hypoxanthine levels were lower compared to HD counterparts. Total purine content of MS beef did not differ from HD beef, whereas the purine content of MS veal was slightly higher than HD veal. It would appear that the addition of MS products to the diet would not significantly alter total purine consumption and hence should pose no risk to hyperuricemic individuals. INTRODUCTION MECHANICALLY SEPARATED (Spkies) [MS (S)] is made by mechanically removing most of the bone from the attached skeletal muscle of livestock carcasses and parts. It was formerly known as Mechanically Processed (Species) Product, and is commonly referred to as mechanically de- boned meat. MS(S) is different from “meat” because it contains small amounts of bone, including bone marrow. The addition of bone marrow has been reported to signifi- cantly elevate the nucleic acid content of MS beef (Arasu et al., 1981). Dietary nucleic acids, due to their purine con- tent, may elevate serum uric acid levels and therefore are thought to be a health risk for hyperuricemic individuals. The amounts of individual purines in MS beef and veal have not been reported. We therefore conducted nucleic acid, purine and proximate analyses of MS and hand deboned (HD) beef and veal products in order to verify the single report of elevated nucleic levels and measure the levels of individual purines in MS(S). MATERIALS&METHODS IN AUGUST, 1981, four commercial palms in the United States were manufacturing MS(S). Three plants were producing MS beef and one plant was producing MS veal. Meat samples were taken from the processing line both prior to HD and after mechanical separation (MS) at each of the four plants. - Coded samples were analyzed for moisture, protein and fat by Chemistry Laboratory Guidebook methods 3.001. 3.002 and 3.003 respectively (FSIS). Ash was determined after 12 hr combustion at 55O’C (FSIS). Nucleic acids were extracted by the Schmidt and Thanhauser method as modified bv Munro and Fleck (1969). DNA and RNA were determined by the procedures of Ceriotti (1952) and Munro and Fleck (1966) respectively. Aliquots of food samples were digested to convert all purine compounds to free bases according to the method of Clifford and Story (1976). Purine bases were then analyzed using high pressure liquid chromatography by the following method. After centrifuga- Authors Savaiano, Salati and Rosamond are with the Dept. of Food Science & Nutrition, Univ. of Minnesota, St. Paul, MN 55108. Au- thors Salinsky and Willis are with the USDA Food Safety & Inspec- tion Service, Athens, GA 30604 and Washington, DC 20250, respec- tively. 1356-JOURNAL OF FO’OD SCIENCE-Volume 48 (1983) tion at 10,000 x g for 20 min, supernatant samples were neutral- ized to pH 5 with 1N NaOH. Samples were injected onto a C-18 reverse phase PBondapak column (Waters Assoc. 3.9 x 300 mm, 10~ pore size). Separations were performed isocratically with 0.2M NH4HzP04. Bases were detected at 254 nm and absorbance peaks were quantified using a Hewlett-Packard model 3380A integrator. Separation of purines was extremely pH sensitive. Adenine (A) and xanthine (X) separated at pH 4.1 while hypoxanthine (H) and guanine (G) co-chromatographed. H and G separated at pH 3.85 while A and X co-chromatographed. Therefore, two separations were used. A and X separated using a flow rate of 1.0 ml/min where- as a separation of H and G was obtained at 0.4 ml/min. Purity of purine separation was assessed by comparing the ratios of 254 nm to 280 nm absorbance of food samples to purine standards (Sigma Chemical Company, St. Louis, MO). _._. ~. Statistical calculations were performed using the Statistical Analysis System (SAS) programs (Barr and Goodnight, 1979). RESULTS&DISCUSSION THE AMOUNTS OF THE PRUIENS, nucleic acids and proximate components in MS and HD beef and veal prod- ucts are shown in Table 1. MS beef and veal contained higher amounts of adenine, guanine and xanthine and lower amounts of hypoxanthine than did their HD counterparts (p < 0.05). Total purine content was higher in MS as com- pared to HD veal (p < 0.05) but did not differ between MS and HD beef products. Amounts of DNA and total nucleic acids were higher in both MS as compared to HD products (p < 0.05). RNA was higher in MS as compared to HD beef (p < 0.05) but did not differ between MS and HD veal products. MS beef and veal products contain less protein and water and more fat and ash than respective HD products (Table 1). A portion of the higher fat content of MS(S) can be attributed to the addition of marrow. All MS products met the USDA-FSIS standards for 14% minimum protein and 30% maximum fat. Fat content of HD products was low, 1.9 and 4.1% for veal and beef, respectively. This fat content is no greater than the fat content of separable lean beef and indicates that the HD products were almost pure muscle. Upon initial review of the data, it was apparent that the HD beef samples from one plant had been improperly col- lected. The ash and fat content for these samples differed markedly from expected levels, and from the content of other HD samples. Therefore, data from these samples were omitted from all statistical evaluations. The ratios of the geometric means for nucleic acids and purines in MS compared to HD beef and MS compared to HD veal are presented in Table 2 in order to indicate the magnitude of the differences between products. The amounts of guanine, DNA and total nucleic acids in MS beef were more than twice those of HD beef whereas the amounts of hypoxanthine in MS beef and veal were less than one-half of those in HD beef and .veal. All other ratios were between 1.0 and 2.0. The ratio of the purine content of MS as compared to HD veal was only 1.19 indicating a modest difference. Data presented here confirm the findings of Arasu et al. (1981) that MS products contain more nucleic acids than HD products. But the absolute amount of total nucleic